1. Field of the Invention
This invention relates to cameras, and particularly with view finders that also serve as light projection arrangements for distance measurements between the camera and an object.
2. Description of the Prior Art
Cameras with conventional automatic focusing mechanisms use triangulation systems in which imaging optics at one end of the base line cooperate with a movable mirror with other imaging optics at the other end of a base line such that moving the mirror to make the two images coincide allows one to obtain the distance to the object from the angle of the mirror. In another known system, a signal is emitted from the camera and the distance to the object is obtained from the angle of the signal returned from the object. Other than ultrasonic systems, such range finding mechanisms or automatic focusing mechanisms need two optical windows, one for projecting light and another for sensing returned light. Furthermore, aside from the window for a taking lens, one more window would be needed for an Alberda view finder, or two more windows for a mark system view finder. Thus, altogether four or five windows must be provided in autofocus blade-shutter cameras. Recently, very compact cameras have been brought on the market. The space on these cameras is so limited that it is difficult to provide four or five windows on their front surfaces. Moreover, when the base line of the automatic focusing device is made short, the accuracy of the distance measurement is decreased. Therefore, it is difficult to manufacture compact cameras with built in automatic focusing devices.